Voltage Dependence of Carbon - Based Supercapacitors for Pseudocapacitance Quantification

In order to understand the participation of electrical double layer and pseudocapacitance to the overall behavior of supercapacitors, a new approach to the analysis of the electrochemical data is proposed. Both the variation of the specific capacitance values and the dependence of these values with the operating voltage window (varying from 0-0.2 V to 0-1 V) were evaluated and used to quantify the contribution arising from each mechanism of energy storage to the total capacitance of the system. The suitability of the methodology here proposed was tested in various carbon materials (multiwalled carbon nanotubes, a carbon aerogel and two activated carbons), different both in nature and physicochemical characteristics. For all of the carbons studied, the capacitance with an exclusive faradic and non faradic origin was quantified. Whereas some of the carbons studied showed a behavior close to an ideal Electrical Double Layer Capacitor (EDLC) with virtually no pseudocapacitance contribution (case of the carbon nanotubes), others presented up to a 40 % of pseudocapacitance contribution (case of KOH activated carbon).